Luteotrophic and luteolytic actions of LH in hypophysectomized, pseudopregnancy rabbits.

Abstract

The ability of LH to sustain the structure and function of corpora lutea (CL) for one week after hypophysectomy was studied in 95 pseudopregnant rabbits. When administered in large sc doses, 125 or 250 μg twice daily (b.i.d.), LH consistently failed to maintain CL regardless of whether the treatment was initiated between 2 to 3 or at 12 hr after hypophysectomy. FSH likewise failed to maintain the CL, although doses of either 200 or 300 μg b.i.d. prevented follicular regression. When smaller doses of LH were combined with FSH, luteal structure and function were maintained to a variable extent and the degree of maintenance was directly related to the weight of the ovary at autopsy. Since luteal maintenance in the rabbit depends on estrogen, these data suggest that small doses of LH, which sustain estrogen secretion from follicular tissue, will be luteotrophic. Larger doses of LH, which suppress estrogen secretion either by luteinization of follicles or by depletion of cholesterol esters, will be luteolytic. Hysterectomy alone did not prevent luteal regression following hypophysectomy, but a higher incidence of good luteal maintenance was obtained with the LH-FSH treatment in hypophysectomized- hysterectomized rabbits than in hypophysectomized rabbits with intact uteri. Although this finding might reflect the removal of a uterine luteolytic factor, it could also be due to the “sparing” of estrogen after removal of its major target organ. (Endocrinology89: 513, 1971)